Paint Calculator
Measure walls and ceilings, adjust your product coverage, and estimate paint to use and cans to buy. Keep colors and primer in separate groups.
Group rooms by color and product. Paint and primer are rounded separately. Defaults are an example; use your measurements and product label.
Product 1
Example · edit your measurements
Wall paint
- Net surface area
- 32.4 m²
- Required with allowance
- 7.128 L
- Cans to buy
- 3
- Purchase volume
- 7.5 L
- Volume above requirement
- 0.372 L
- Known material cost
- Price not entered
Displayed quantities are rounded; package counts use full precision. Use the same currency for all prices. Labor, preparation, tools, tax and delivery are excluded. Product groups are rounded independently; areas in a group are summed first.
From quantity to appearance
Choose a wall color
Only the selected material or color enters the design brief. Cans, boxes and cost stay in this calculation. The preview shows a design direction, not installation specifications.
How much paint do I need?
Paint needed = net area × coats × (1 + extra allowance / 100) ÷ coverage per coat. Cans to buy = round up paint needed ÷ can capacity. Coverage depends on your product, surface and application method. Enter the product label’s rate; defaults are editable examples.
Wall and ceiling area
For a rectangular room, wall area = 2 × (length + width) × height. A flat ceiling is length × width. Choose walls, ceiling, or both for each room. Use a separate product group when a ceiling uses different paint. Irregular surfaces need separate measured rectangles or a separately measured room approximation.
Door and window deductions
Enter the measured area you will not paint. This includes doors, windows and other openings. Do not deduct a door if you are painting it with the same wall product. Openings cannot equal or exceed the wall area. Ceiling-only calculations ignore wall openings.
Paint coverage, coats and primer
Coverage is per coat. Two coats and 10% extra are example settings, not universal instructions. Primer is calculated and rounded separately using its own coats, coverage and can size; the primer option assumes the same surface area. Group differently if only part of a room needs primer.
Liters, US gallons and material cost
One US liquid gallon is 3.785411784 liters. Imperial units here use US gallons, not UK gallons. A price is optional and refers to one can in your own currency. Missing prices leave the overall budget incomplete; labor, tools, tax and delivery are excluded.
A worked room example
For a 4 × 3 m room, 2.6 m high, with 4 m² of openings, the net wall area is 32.4 m². At two coats, 10% extra and 10 m²/L per coat, you need 7.128 L. With 2.5 L cans, buy three cans (7.5 L). Multiple rooms using one product are summed before rounding.
Frequently asked questions
How much paint for a 12 × 12 room?
Wall height, openings, coats and coverage must also be specified. At 9 ft high with 63 ft² of unpainted openings, walls total 369 ft². Two coats, 10% extra and 350 ft² per US gallon require about 2.32 gallons, or three 1-gallon cans. This example excludes the ceiling.
Does this include the ceiling?
Only when you choose Ceiling or Walls + ceiling. If the ceiling has a different color or product, put it in a separate group so quantities and cans are not mixed.
How much does a gallon cover?
Use the actual product label and its coverage per coat. Porosity, texture, color changes and application method affect coverage. A generic rate is a starting assumption, not a purchase guarantee.
Can I estimate painting labor?
This tool estimates quantities and material cost using your prices. It does not estimate labor or local contractor rates. Use a trade quote for preparation and application.
Method and rule notes
The linked guides inform the starting suggestions. Your editable measurements and product values determine the result.
Rule notes reviewed October 12, 2026.